Studies are being performed on the neurochemical aspects of selective vulnerability induced by short-term ischemia. The CA 1 neurons of the hippocampus have been shown to disappear by 96 hours after 5 minutes of bilateral ischemia in the gerbil brain. This observation provides a model for the examination of the neurochemical events which lead up to the selective loss of neurons. Metabolites were measued in the CA 1 and CA 3 of the hippocampus and in the cerebral cortex. Marked changes in the levels of glycogen, glucose, GABA and glutamate were evident between 1.5 and 48 hours of recirculation. However, these changes were essentially uniform in the 3 regions examined. By 96 hours of postischemia, the metabolite concentrations in the CA 1 regions were substantially different than the other two regions which could be attributed to the infiltration of glia. The only differences between the CA 1 region and the other 2 regions were an elevation of cyclic GMP and a depression of cyclic AMP which occurred at 6 hours of recirculation. The 6 hours period appears to be critical to the eventual loss of the CA 1 neurons.